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Why aren’t BNC jacks common?

Digital connection between a source component and DAC calls for typically other a 75 ohm impedance or 110 ohm impedance cable. Sourcing a 110 ohm cable is easy- it’s very common. But a 75 ohm cable? Not so much primarily because just about every RCA terminated cable is not a 75 ohm cable, however, true 75 ohm cable is a snap with BNC terminations. BNC is not expensive and arguably it’s a more secure connection than is RCA. I therefore do not understand why components with BNC jacks are very rare. Perhaps you can argue the ommission of a BNC connection is justified on mass market gear but on high end gear?  Can someone provide an explanation that makes at least some sense? My DAC supports BNC (Bricasti) but my CD transport (Simaudio) does not. Thanks!! 

zavato
zavato's avatar
zavato OP
1,483 posts
 

@mitch2 it is a 2 foot punt, making it all the more inexplicable. I do t know how a high end company can in good faith offer a 75 ohm point of connection and not use BNC. 

mitch2
4,731 posts
 

I have owned multiple high'ish end DACs and very few of them had BNC connectors.  The adaptors may "work" to conduct a signal but in the audio world where I constantly read about how "everything matters" it perplexes me how something like this that is so simple to get right doesn't adhere to some sort of standard. FWIW, AI says,

BNC/RCA adaptors on a 75-ohm digital cable technically introduce an impedance mismatch, as BNC/RCA connectors are not designed for true 75-ohm impedance. While the cable itself remains 75-ohm, RCA connectors are generally around 50 ohms or non-impedance-controlled.  Therefore, the connector transition can create small signal reflections. However, at typical S/PDIF frequencies and short cable lengths, this mismatch is often negligible.

I have gone back to using USB connectors into both of the DACs in my main system, because IMO they sound better.

 

zlone
1,321 posts
 

This has baffled me as well, BNC is such a superior connection. I don’t use SPDIF in my system anymore, but I always had either BNC or AES as a requirement when I did.

zavato's avatar
zavato OP
1,483 posts
 

@zlone in my system I run two digital components into my DAC, one is a streaming transport and the other is a CD transport. Both have AES outputs and RCA based SPDIF outputs plus toslink. The streamer also has a usb output. My DAC has an aes input, rca/SPDIF input, BNC/SPDIF input, usb input and toslink. I am not a huge fan of usb or toslink, so I am left with SPDIF and aes. My streamer feeds the dac via aes and cd feeds the dac with a cable that is rca on one end and BNC on the other end. 

zlone
1,321 posts
 

My streamer feeds the dac via aes and cd feeds the dac with a cable that is rca on one end and BNC on the other end

That is unfortunate that you have to use an adapter. I never liked USB that much, but I eventually came around to it as my equipment and cabling progressed. 

I see that you have a Bricasti DAC. I recently acquired an M3 with the network card and have switched to using that input as a Roon endpoint, it far exceeds the performance of the other inputs on the DAC. 

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